The present invention pertains to a breathing gas mixture and to a device for metering a breathing gas mixture.
Various breathing gas mixtures, which may be used for various applications in medicine, have been described in the literature. For example, U.S. Pat. Ser. No. 5,228,434 discloses a breathing gas mixture containing xenon, oxygen and helium, which is said to be used in anesthesia.
Liquid perfluorocarbons were hitherto introduced into the lungs of a human patient or mammal for the treatment of lung diseases associated with severe gas exchange disturbances, especially ARDS (Adult Respiratory Distress Syndrome) and pneumonia, and the patient or the mammal was respirated by means of a conventional respirator during that time.
It was observed that perfluorocarbons are able, in principle, to substantially improve the gas exchange and especially the O2/CO2 exchange in the lungs.
However, one fundamental problem of the current clinical use of liquid perfluorocarbons is the fact that it is not possible to accurately meter the liquid perfluorocarbons. In addition, increased respiration pressures are necessary for respirating the partially liquid-filled lungs, as a result of which adverse effects may in turn be induced in the patient.
The object of the present invention is to provide a breathing gas mixture for the treatment of lung diseases and a device for metering same in order to make possible an improved, accurate and reproducible metering for the treatment of lung diseases.
According to the invention, a breathing gas mixture is provided containing an amount of perfluorocarbon and oxygen with 5 vol. % to 40 vol. % relative to the amount of perfluorocarbon and oxygen. The percentage of perfluorocarbon and oxygen in the breathing gas mixture is preferably about 20 vol. % to 100 vol. % of the breathing gas mixture and the remaining part of up to about 80 vol. % preferably contains one or more of the gases nitrogen, nitrogen monoxide and/or one or more anesthesia gases or noble gases, especially xenon. The perfluorocarbon preferably comprises one or more of the compounds perfluoropentane, perfluorohexane, and perfluorooctane, wherein perfluoropentane or perfluorohexane is especially preferred.
According to another aspect of the invention, a device is provided for metering a breathing gas mixture as mentioned above. The device has one or more evaporators connected in series for evaporating the liquid perfluorocarbon. There is a gas flow connection to an inspiration line of an anesthesia apparatus or respirator, which gas connection is arranged downstream of the evaporator or evaporators.
A measuring cell is preferably provided for determining the concentration of the perfluorocarbon in the breathing gas mixture. The concentration signal is used to set the perfluorocarbon concentration in the breathing gas mixture via one or more final control elements at the evaporator or evaporators, especially after comparison with corresponding set points. The measuring cell for determining the concentration of the perfluorocarbon in the breathing gas mixture may be an optical measuring cell based on infrared absorption spectroscopy, wherein is it used both to measure the inspiratory gas mixture in the inspiration line and to measure the expiration gas mixture in the expiration line.
A central measuring and control unit is preferably provided that has final control elements at the evaporator or evaporators to set the perfluorocarbon/oxygen concentration in the inspiratory breathing gas mixture as a function of the perfluorocarbon concentration in the inspiratory and/or expiratory breathing gas mixture. An additional gas-metering unit may be provided for metering one or more additional gases to the inspiratory breathing gas mixture, wherein the metering is set via the measuring and control unit.
An essential advantage of the present invention is that perfluorocarbons with their favorable properties can be used specifically and reproducibly for the treatment of lung diseases.
Completely fluorinated, i.e., hydrogen-free fluorocarbons are also called perfluorinated fluorohydrocarbons or perfluorocarbons (PFC) for short.
These compounds are highly stable and behave almost like noble gases of a similar mass. Advantageous physiological properties were reported in mammals, so that the controlled use is desirable in humans as well.
The breathing gas mixture according to the invention contains an amount of gaseous or vapor-like perfluorocarbon and oxygen with 5 vol. % to 40 vol. % and especially 10 vol. % to 20 vol. % of perfluorocarbon relative to the amount of perfluorocarbon and oxygen in the breathing gas mixture.
The amount corresponding to the sum of perfluorocarbon and oxygen in the breathing gas mixture is about 20 vol. % and, in the extreme case, 100 vol. %, and the rest, amounting to a maximum of about 80 vol. %, contains one or more of the gases nitrogen, nitrogen monoxide and/or one or more anesthesia gases or noble gases, especially xenon.
The preferred perfluorocarbons according to the present invention are perfluoropentane, perfluorohexane, perfluorooctane, alone or as a mixture, and especially perfluorohexane.
It is essential for the present invention that the perfluorocarbons used are used in the form of gases or vapors.
Besides the perfluorocarbons mentioned, it is also possible to use perfluoro-Decalin and perfluorooctyl bromide.
Based on their physicochemical properties (boiling point, vapor pressure), perfluorohexane is best suited for evaporation at usual room temperatures and thus for the use according to the present invention, because the evaporation behavior of perfluorohexane is similar to that of the anesthetics used in clinical practice.
From this arises the great advantage that components that are, in principle, available and may be used in the configurations known from anesthesia may be used for a device for administering a breathing gas mixture according to the present invention.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which preferred embodiments of the invention are illustrated.